The present invention relates to an electrostatic recording apparatus wherein an image carrier is cleaned by a cleaning blade, and to a cleaning blade used for the electrostatic recording apparatus.
In an electrostatic recording apparatus, an electrostatic image is formed on an image carrier such as an electrophotographic photoreceptor and it is developed to become a toner image, then it is transferred onto a transfer sheet and fixed thereon to become a toner image, while the surface of the image carrier on which image forming has been completed is cleaned by a cleaning device to be ready for subsequent image forming.
The cleaning device used commonly is a blade cleaning device which has an excellent cleaning efficiency. However, it has a problem that blade curling or chipped blade edges are caused in the contact between the cleaning blade edge and the image carrier.
In particular, these phenomena tend to be caused on the non-image-forming area. Namely, in the image forming area, toner particles lie between an image carrier and a cleaning blade to function as a lubricant. Therefore, the cleaning blade slides smoothly on the surface of the image carrier. However, it takes considerable time for the toner dammed up by the cleaning blade to move to the portion which is the non-image-forming area.
Therefore, in the initial stage from the start of using a cleaning blade, or under the condition where toner does not move to the non-image-forming area, the coefficient of friction on the non-image-forming area of the image carrier is great, and curling of a cleaning blade, abnormal noises caused by vibration and chipped blade edges tend to be caused.
There are some cases where a light-sensitive layer is not coated all over the circumferential surface of an image carrier, and a base body of the image carrier is exposed at the end portion of the image carrier in the crosswise direction. In such a case, the coefficient of friction on the portion where the base body is exposed is greater than that on the portion where the light-sensitive layer is coated. Therefore, it is hard for an end portion of the cleaning blade which is in contact with the portion where the base body is exposed to slide on the surface of the image carrier smoothly, compared with the portion which is inside the end portion.
In this case again, therefore, curling of a cleaning blade, abnormal noises caused by vibration and chipped blade edges tend to be caused.
To cope with the foregoing, there have been suggested following technologies. For example, TOKKAIHEI No. 6-332350 discloses that rounding or chamfering is formed on a blade edge. Further, TOKKAISHO No. 61-212881 discloses that a cleaning blade does not come in contact with an image carrier. It is further disclosed by TOKKAIHEI No. 5-150696 that the coefficient of friction on the surface of an image carrier is lowered. Further, TOKKAISHO No. 55-77773 and TOKKAIHEI No. 4-212190 disclose that a cleaning blade is coated with a film layer, and low friction and durability of the film layer for exfoliation are improved. In addition to the foregoing, there has been put to practical use the technology to reduce the coefficient of friction by applying a lubricant such as polyfluorovinylidene powder or toner on both ends of a cleaning blade or by providing Teflon coating on both end portions of a cleaning blade.
As stated above, lubricating property is secured by coating lubricant or toner on edge portions on both ends of a cleaning blade, in general, but its effect does not last for a long time. In TOKKAISHO No. 61-212881, on the other hand, it is difficult to secure sealing property against toner scattering. Though TOKKAIHEI No. 5-150696 discloses a technology to lower the coefficient of friction on the surface of an image carrier, the structure thereof is complicated, resulting in cost increase. Though TOKKAISHO No. 55-77773 and TOKKAIHEI No. 4-212190 disclose a technology to provide a film layer on a cleaning blade to realize low friction, there are problems in exfoliation and durability of the film layer. Though TOKKAIHEI No. 6-332350 discloses a cleaning device and a manufacturing method for the same wherein rounding or chamfering is formed on an edge portion, there are problems that the rounding or chamfering is for the entire portions of the cleaning blade, the chamfering width is not sufficient for the curling, and it is not easy to manufacture cleaning blades.